Recent genetic studies of Alzheimer?s disease (AD) have focused our attention on the role of the innate immune system in disease susceptibility. However, the exact mechanism by which genetic variants dysregulate resident microglial cells and infiltrating monocytes that differentiate into macrophages to contribute to the development of AD remains unclear. Myeloid cells (microglia and macrophage) are highly plastic, responding to their environment to fulfill different functions that include the development and maintenance of synapses, control of inflammation and repair of the central nervous system (CNS) parenchyma. Emerging data highlight the heterogeneity of these cells that has, until now, been largely defined morphologically. In this application, we generate a new resource for the Alzheimer disease community: a collection of purified, cryopreserved aged human microglia from AD and non-AD brains that can be requested by ADRC and other investigators to support the investigation of a critical cell type for which access to live primary human cells has been an important limitation for the field.